Breast Cancer Risk Factors: Birthweight

Studies show women with a higher birthweight (a woman’s weight when she was born) have an increased risk of breast cancer, especially before menopause, compared to women with a lower birthweight [56-61].

A higher birthweight doesn’t appear to be linked to higher estrogen levels in adulthood [62-64]. However, birthweight may be a marker of factors related to growth that are linked to breast cancer risk, such as adult height [63,65-66].

Other reasons behind the link between birthweight and breast cancer risk are under study.

Learn about other early life exposures and breast cancer risk.

For a summary of research studies on birthweight and breast cancer risk, visit the Breast Cancer Research Studies section.

Learn about other factors linked to the risk of breast cancer.

1. Know your risk

Talk with both sides of your family to learn about your family health history.
Talk with a health care provider about your risk of breast cancer.

2. Get screened

Talk with a health care provider about which screening tests are right for you if you’re at higher risk.
Have a mammogram every year starting at age 40 if you’re at average risk.*
Have a clinical breast exam at least every 3 years starting at age 25, and every year starting at age 40.*

* Per National Comprehensive Cancer Network Guidelines

3. Know what is normal for you

See a health care provider if you notice any of these breast changes:

Lump, hard knot or thickening inside the breast or underarm area
Swelling, warmth, redness or darkening of the breast
Change in the size or shape of the breast
Dimpling or puckering of the skin
Itchy, scaly sore or rash on the nipple
Pulling in of the nipple or other parts of the breast
Nipple discharge that starts suddenly
New pain in one spot that doesn’t go away

To see illustrations of these warning signs, please visit the Warning Signs of Breast Cancer page.

4. Make healthy lifestyle choices

Maintain a healthy weight.
Make exercise part of your routine.
Limit alcohol intake.
Limit menopausal hormone therapy (postmenopausal hormone use).
Breastfeed if you can.

Updated 12/17/24

This content is regularly reviewed by an expert panel including researchers, practicing clinicians and patient advocates.

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